Question about dual layer DVD media (geek question)

I have a large program that will need to be burned to a DL DVD.

I have a regular external DVD drive - but can it burn both sides? Or do I have to flip the disk over?

(I never have done this before).

Or maybe I should put it on a large USB flash drive...but it's an ISO. Will it still load?

I need the ABCs here.

Thanks! :)

It depends on the program, but if the only intent is to copy to from one hard drive to another, a USB stick would certainly be easier than burning a DVD!